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[Qemu-block] [PATCH v3 20/39] qcow2: Update qcow2_get_cluster_offset() t
From: |
Alberto Garcia |
Subject: |
[Qemu-block] [PATCH v3 20/39] qcow2: Update qcow2_get_cluster_offset() to support L2 slices |
Date: |
Fri, 26 Jan 2018 16:59:47 +0200 |
qcow2_get_cluster_offset() checks how many contiguous bytes are
available at a given offset. The returned number of bytes is limited
by the amount that can be addressed without having to load more than
one L2 table.
Since we'll be loading L2 slices instead of full tables this patch
changes the limit accordingly using the size of the L2 slice for the
calculations instead of the full table size.
One consequence of this is that with small L2 slices operations such
as 'qemu-img map' will need to iterate in more steps because each
qcow2_get_cluster_offset() call will potentially return a smaller
number. However the code is already prepared for that so this doesn't
break semantics.
The l2_table variable is also renamed to l2_slice to reflect this, and
offset_to_l2_index() is replaced with offset_to_l2_slice_index().
Signed-off-by: Alberto Garcia <address@hidden>
Reviewed-by: Eric Blake <address@hidden>
---
block/qcow2-cluster.c | 30 +++++++++++++++---------------
1 file changed, 15 insertions(+), 15 deletions(-)
diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c
index 416d48fa77..128a82dc5a 100644
--- a/block/qcow2-cluster.c
+++ b/block/qcow2-cluster.c
@@ -530,8 +530,8 @@ int qcow2_get_cluster_offset(BlockDriverState *bs, uint64_t
offset,
{
BDRVQcow2State *s = bs->opaque;
unsigned int l2_index;
- uint64_t l1_index, l2_offset, *l2_table;
- int l1_bits, c;
+ uint64_t l1_index, l2_offset, *l2_slice;
+ int c;
unsigned int offset_in_cluster;
uint64_t bytes_available, bytes_needed, nb_clusters;
QCow2ClusterType type;
@@ -540,12 +540,12 @@ int qcow2_get_cluster_offset(BlockDriverState *bs,
uint64_t offset,
offset_in_cluster = offset_into_cluster(s, offset);
bytes_needed = (uint64_t) *bytes + offset_in_cluster;
- l1_bits = s->l2_bits + s->cluster_bits;
-
/* compute how many bytes there are between the start of the cluster
- * containing offset and the end of the l1 entry */
- bytes_available = (1ULL << l1_bits) - (offset & ((1ULL << l1_bits) - 1))
- + offset_in_cluster;
+ * containing offset and the end of the l2 slice that contains
+ * the entry pointing to it */
+ bytes_available =
+ ((uint64_t) (s->l2_slice_size - offset_to_l2_slice_index(s, offset)))
+ << s->cluster_bits;
if (bytes_needed > bytes_available) {
bytes_needed = bytes_available;
@@ -574,17 +574,17 @@ int qcow2_get_cluster_offset(BlockDriverState *bs,
uint64_t offset,
return -EIO;
}
- /* load the l2 table in memory */
+ /* load the l2 slice in memory */
- ret = l2_load(bs, offset, l2_offset, &l2_table);
+ ret = l2_load(bs, offset, l2_offset, &l2_slice);
if (ret < 0) {
return ret;
}
/* find the cluster offset for the given disk offset */
- l2_index = offset_to_l2_index(s, offset);
- *cluster_offset = be64_to_cpu(l2_table[l2_index]);
+ l2_index = offset_to_l2_slice_index(s, offset);
+ *cluster_offset = be64_to_cpu(l2_slice[l2_index]);
nb_clusters = size_to_clusters(s, bytes_needed);
/* bytes_needed <= *bytes + offset_in_cluster, both of which are unsigned
@@ -611,14 +611,14 @@ int qcow2_get_cluster_offset(BlockDriverState *bs,
uint64_t offset,
case QCOW2_CLUSTER_UNALLOCATED:
/* how many empty clusters ? */
c = count_contiguous_clusters_unallocated(nb_clusters,
- &l2_table[l2_index], type);
+ &l2_slice[l2_index], type);
*cluster_offset = 0;
break;
case QCOW2_CLUSTER_ZERO_ALLOC:
case QCOW2_CLUSTER_NORMAL:
/* how many allocated clusters ? */
c = count_contiguous_clusters(nb_clusters, s->cluster_size,
- &l2_table[l2_index], QCOW_OFLAG_ZERO);
+ &l2_slice[l2_index], QCOW_OFLAG_ZERO);
*cluster_offset &= L2E_OFFSET_MASK;
if (offset_into_cluster(s, *cluster_offset)) {
qcow2_signal_corruption(bs, true, -1, -1,
@@ -634,7 +634,7 @@ int qcow2_get_cluster_offset(BlockDriverState *bs, uint64_t
offset,
abort();
}
- qcow2_cache_put(s->l2_table_cache, (void **) &l2_table);
+ qcow2_cache_put(s->l2_table_cache, (void **) &l2_slice);
bytes_available = (int64_t)c * s->cluster_size;
@@ -652,7 +652,7 @@ out:
return type;
fail:
- qcow2_cache_put(s->l2_table_cache, (void **)&l2_table);
+ qcow2_cache_put(s->l2_table_cache, (void **)&l2_slice);
return ret;
}
--
2.11.0
- [Qemu-block] [PATCH v3 27/39] qcow2: Update qcow2_update_snapshot_refcount() to support L2 slices, (continued)
- [Qemu-block] [PATCH v3 27/39] qcow2: Update qcow2_update_snapshot_refcount() to support L2 slices, Alberto Garcia, 2018/01/26
- [Qemu-block] [PATCH v3 04/39] qcow2: Remove BDS parameter from qcow2_cache_get_table_idx(), Alberto Garcia, 2018/01/26
- [Qemu-block] [PATCH v3 01/39] qcow2: Fix documentation of get_cluster_table(), Alberto Garcia, 2018/01/26
- [Qemu-block] [PATCH v3 34/39] qcow2: Rename l2_table in count_contiguous_clusters_unallocated(), Alberto Garcia, 2018/01/26
- [Qemu-block] [PATCH v3 17/39] qcow2: Update l2_allocate() to support L2 slices, Alberto Garcia, 2018/01/26
- [Qemu-block] [PATCH v3 20/39] qcow2: Update qcow2_get_cluster_offset() to support L2 slices,
Alberto Garcia <=
- [Qemu-block] [PATCH v3 32/39] qcow2: Rename l2_table in qcow2_alloc_compressed_cluster_offset(), Alberto Garcia, 2018/01/26
- [Qemu-block] [PATCH v3 06/39] qcow2: Remove BDS parameter from qcow2_cache_entry_mark_dirty(), Alberto Garcia, 2018/01/26
- [Qemu-block] [PATCH v3 35/39] qcow2: Rename l2_table in count_cow_clusters(), Alberto Garcia, 2018/01/26
- [Qemu-block] [PATCH v3 28/39] qcow2: Read refcount before L2 table in expand_zero_clusters_in_l1(), Alberto Garcia, 2018/01/26
- [Qemu-block] [PATCH v3 38/39] iotests: Test downgrading an image using a small L2 slice size, Alberto Garcia, 2018/01/26
- [Qemu-block] [PATCH v3 31/39] qcow2: Update qcow2_truncate() to support L2 slices, Alberto Garcia, 2018/01/26